Woven or knitted fabrics coated with a resin such as Poly-Vinyl Chloride (PVC), polytetrafluorethylene (PTFE), urethane or other suitable resin have been used to provide structures. The fibers or fiber bundles of the woven fabric are coated with a resin, thereby forming a matrix surrounding the fibers. The matrix material is typically the medium, by which seams in the construction, can transfer load across the joints in the fabric. One example of such a structure is a radome, which is a dome shaped protective housing used to cover a radar antenna. A radome may be subject to a severe set of conditions such as supporting heavy loads for extended periods of time at extreme temperatures and humidity.
Traditional fabric structures apply resin-based coatings to the fabric substrate via ‘knife-over-roll’ or film lamination techniques. In order to take structural advantage of a fiber structure, applied loads should be able to transfer from one fiber bundle to another and the full load capability of the fabric should be able to be transferred across joints in the fabric. The resin system applied to the fabric assists with load transfer. However, the effectivity of this load transferring ability is directly related to the interface between the fiber and the resin. This interface is dependent both on the volume of surface contacted, the linkage between the fiber surface and the resin, and the resin properties. When a fabric is coated with resin, the coating is only in contact with the exposed outer surface of the fiber bundles and, effectively, the fiber/resin product (also referred to as the fabric product) is full of voids or air pockets within the fiber bundles. When an applied load encounters a void, the load cannot be transferred or carried from fiber filament to filament. The propagation of the load effectively stops and a stress concentration develops that eventually exceeds the fabric load resistance, resulting in a failure of the fabric product. This effect is most pronounced at the fabric seam locations where the fiber bundles are not continuous across the joint.
A drawback associated with these coated woven fabrics and seams is that when they are utilized to provide a structure such as a radome, they typically do not withstand the long duration, high level working loads and extreme environmental conditions.
One attempt to resolve the above-mentioned drawback was to increase the base fabric load carrying capability, load transfer capability and fiber bundle load sharing capability by modifying existing fabric weave designs. These attempts did not produce a fabric/seam system product, which could withstand the working loads and environmental conditions mentioned above. Another attempt to overcome the above mentioned drawback involved development of new fabric/fiber technology. Although this attempt utilized innovative fiber and fabric designs, this attempt relied on traditional fabric coating technology that failed to achieve the required combination of properties between the fiber system and the resin matrix, resulting in premature seam failure. The net result of both attempts was unacceptable operation in the area of seam performance of the structure.